api docs: Fix blank line at end of Code Blocks.
api docs: Fix blank line at end of Code Blocks.

Added the missing padding: 0 to remove the blank line in code blocks
as is done in Webapp code blocks CSS. Fixes part of #15967.

zulip/zulip,kou/zulip,eeshangarg/zulip,kou/zulip,kou/zulip,punchagan/zulip,hackerkid/zulip,eeshangarg/zulip,zulip/zulip,andersk/zulip,andersk/zulip,zulip/zulip,rht/zulip,hackerkid/zulip,punchagan/zulip,hackerkid/zulip,zulip/zulip,kou/zulip,hackerkid/zulip,zulip/zulip,rht/zulip,eeshangarg/zulip,kou/zulip,andersk/zulip,andersk/zulip,eeshangarg/zulip,punchagan/zulip,eeshangarg/zulip,eeshangarg/zulip,punchagan/zulip,rht/zulip,rht/zulip,andersk/zulip,kou/zulip,andersk/zulip,rht/zulip,rht/zulip,punchagan/zulip,rht/zulip,hackerkid/zulip,zulip/zulip,hackerkid/zulip,punchagan/zulip,zulip/zulip,andersk/zulip,kou/zulip,eeshangarg/zulip,punchagan/zulip,hackerkid/zulip